Variable condenser control



June 9, 1931. M. H. BENNETT 1,809,371

VARIABLE CONDENSER CONTROL Filed J ly 7, 1927 Patented June 9, 1931' UNITED sTA'rss eeann earner ersicE MORRIS H. BENNETT, or WAT RBURY, CONNECTICUT; ASSIGNOR 'ro soov riir MANU- FAC'I'URING COMPANY, or wArnnBUn CONNECTICUT, A oonronarion or con- Application filed July 7,

This invention relates to controls for variable condensers and more particularly to controls for radio condensers of the Vernier type. r

In variable condensers for radio use itis almost impossible to bring the condenser to more than an approximate adjustment with the ordinary direct-connected control dial and it is the usual practice to resort to some form of Vernier dial control in order to ob: tain accurate settings. VVith'such controls arrangement is made by some sort of reducing caring between the control knob and the con enser shafts whereby large adjustments of the knob result in small adjustments of the shaft.

It is, therefore, an object of this invention to provide a Vernier dial control which may be attached to a variable condenser shaft and which may permit setting the condenser accurately to the position desired.

For purposes of illustration there is represented in the accompanying drawings a preferred embodiment of the invention, the features of the'invention being pointed out in the appended claims.

In these drawings Figure 1 is a sectional view through the condenser dial constructed in accordance with the invention;

Figure 2 is a front View thereof, partly broken away to show the relation of the parts; and,

Figure 3 is a view of the pointer used in connection with the dial showing its relation to some of the parts. I

In the construction of a condenser control dial in accordance with this invention a rotor shaft 1 is journalled in a bushing 2 extending through a suitable opening in a panel 3, a lock nut 4 and flange 5 securing the bushing in place. The free end of shaft 1 is centered to freely turn in a bearing 6, the outer surface of which is conical on that portion thereof surrounding shaft 1. This portion of the surface provides a track 7 on which a plurality of friction wheels 8, 9 and 10 are adapted to roll in response to rotation of said bearing. Rigidly mounted on shaft 1, by means of a suitable set screw 11, is an annular member VARIABLE CONDENSER. CONTROL 192?. serial. No.'2l)3,898..

12, having its central portion counter-bored as at 13;. At equally spaced intervals on an nular member 12. are located a number of threaded bores adapted to receive screws 14- whose shanks are surrounded by bushings 15, the outer surfaces of which provide bearings for the wheels 8,9 and 10. Suitably secured to panel and centered about shaft 1 at a distance equal to the diameter of the wheels is an annular cage 16 having an outwardly flared portion 17, the inner surface of which forms a second track for wheels 8, 9, and 10. The angleof flare is such that the inner portion is parallel to the conical surface 7 on hearing 6 so that the wheels will rotate evenly between: the two tracks. i

It is now evident that rotation of bearing 7 causesfriction wheels 8, 9' and 10 to rotate but since the friction surface of the wheels is inengagement with stationary track 17 the result is that the bearings of the wheels will move in an orbit about bear-h1g6, rotating annular member 12 and shaft 1;

Means are provided for rotating'bearing 7 and these means preferably comprise a skirted knob 18 having a central opening 19 to receive a narrowed extension 20. The knob is secured on bearing 6-by means of a screw 21 provided with a washer'22, the screw taking into a centralbore 23 in the bearing.

For indicatingthe setting of the condenser there is provided a pointer 24 cooperating with a scale 25 suitably embossed or stencilled on panel. 3'. Pointer 24 has a number of ex.- tensions 26 corresponding to the number of wheels 8, 9 and. 10, by which extensions it is secured to the wheel bearings 15 and thus to shaft 1 by means of screwsl.

- In order to impart resiliency to the bearing 6 in which shaft 1 is our'nalled, pointer 24 is further provided with an extension 27 adapted to surround the bearing at its outer end to provide an abutment 28 against which a helical spri-ng29 rests. The other end of spring 29 seats against a shoulder 30 on hearing 6, metallic washer 31 and fibrous washer 32 maintaining it in proper position. Spring 29 by exerting its tension against shoulder 30 of bearing 6 and abutment 28 of pointer 24:, (which, it will be remembered, is indirectly secured to shaft 1) tends to maintain the shaft 1 in its bearing 6.

The operation of the dial above described will now be obvious but to summarize:

Turning of the knohlS causes bearing 6 to rotate, thus imparting a frictional drive to wheels 8, 9 and 10 from its outer conical surface 7. Since these wheels are frictionally held against track 17 an orbital movement of their bearings about surface 7 results, thereby rotating annular member 12 and with it, shaft 1. Thus the condenser is set. Pointer 24 be ing securely fastened to the bearings of the wheels moves therewith and indicates accurately the condenser setting in conjunction with scale 25.

Since the relation between the speed of rotation of the knob and that of the shaft depends directly upon the diameter of wheels 8, 9 and 10, any desired speed reduction may be obtained by changing these diameters, changes in size of cage 16 and annular member 12, of course, being made to take care of the new wheel diameters.

\Vhat is claimed is:

1. In a Vernier condenser control, and in combination, a condenser shaft, an annular member fixed on said shaft, screws threaded into the annular member with axes oblique to the axis of the condenser shaft, friction wheels mounted on the screw shanks between the annular member and the screw heads, a bearing free on the end of the shaft and having an outer cone surface for contacting with the wheels, an annular stationary cage concentric with and surrounding the shaft, said cage having at its outer end an internal axially flaring surface forming a track for the Wheels, and means to turn the bearing to frictionally drive the wheels.

2. In a Vernier condenser control and in combination, a condenser shaft, an annular member fixed on said shaft, screws threaded into the annular member with axes oblique to the axis of the condenser shaft, friction wheels mounted on the screw shanks between the annular member and the screw heads, a bearing free on the end of the shaft and having an outer conesurface for contacting with the Wheels, an annular stationary cage c0ncentric with and surrounding the shaft, said cage having at one end an internal axially flaring surface forming a track for the sheels, a pointer fastened beneath the screw heads beyond the cage, and means to turn the hearing tofrictionally drive the wheels.

In testimony whereof, I have hereunto set my hand.

MORRIS H. BENNETT. 

